High-bandwidth nonlinear control for soft actuators with recursive network models
This work provides an incremental improvement in control for soft actuators, enabling more efficient and co-located control systems.
This paper introduces a high-bandwidth nonlinear control technique for soft actuators, combining recursive network models for output prediction with online Newton-Raphson optimization. The method achieves effective spatial trajectory tracking with root mean squared path tracking errors of 1.8mm (FC), 1.62mm (GRU), and 2.11mm (LSTM), while maintaining small model sizes (highest flash memory requirement of 2.22kB).
We present a high-bandwidth, lightweight, and nonlinear output tracking technique for soft actuators that combines parsimonious recursive layers for forward output predictions and online optimization using Newton-Raphson. This technique allows for reduced model sizes and increased control loop frequencies when compared with conventional RNN models. Experimental results of this controller prototype on a single soft actuator with soft positional sensors indicate effective tracking of referenced spatial trajectories and rejection of mechanical and electromagnetic disturbances. These are evidenced by root mean squared path tracking errors (RMSE) of 1.8mm using a fully connected (FC) substructure, 1.62mm using a gated recurrent unit (GRU) and 2.11mm using a long short term memory (LSTM) unit, all averaged over three tasks. Among these models, the highest flash memory requirement is 2.22kB enabling co-location of controller and actuator.